This project seeks to purify and characterize the major classes of growth factors produced and released by transformed cells. This includes chemical and biological comparisons with known hormones like insulin-like growth factor (IGF) and epidermal growth factor (EGF). A low molecular weight polypeptide with multiplication stimulating activity (MSA) was isolated from serum-free media conditioned by a clone of normal Buffalo rat liver cells. MSA is a single-chain polypeptide of 67 residues, with a calculated molecular weight of 7,484, and displays 93% homology wih the functionally related human IGF-II. A human metastatic melanoma cell line (A2058) produces a transforming growth factor (TGF). TGF is functonally related to EGF and interacts with the same receptors on cultured cells. TGF, however, produces a profound phenotypic alteration on susceptible cells and confers the ability to behave as transformed cells. EGF, in contrast, does not produce large, progressively growing cell colonies in soft agar. TGF was isolated from serum-free media conditioned by A2058 cells. A comparison was made with human EGF (hEGF) isolated and purified from human urine.